Let's say we have an elastisearch index, orders, where we store a list of orders for a user. For example:

{
    "username": "user1",
    "orders": [
        {
            "id": "order1",
            "timestamp": "2022-01-01T00:00:00Z",
            "items": [
                {
                    "id": "item1",
                    "name": "item1",
                    "price": 10,
                    "quantity": 1
                },
                {
                    "id": "item2",
                    "name": "item2",
                    "price": 20,
                    "quantity": 2
                }
            ]
        },
        {
            "id": "order2",
            "timestamp": "2022-01-02T00:00:00Z",
            "items": [
                {
                    "id": "item3",
                    "name": "item3",
                    "price": 30,
                    "quantity": 3
                },
                {
                    "id": "item4",
                    "name": "item4",
                    "price": 40,
                    "quantity": 4
                }
            ]
        }
    ]
}

One assumption here: we will be using the username as document id.

When updating a user's order, it can be done in two ways:

Option 1

Calling GET index API to check if that document exists. If exists, then update. If not create the document for that user.

We have this order data for user1:

{
  "username": "user1",
  "order": {
    "id": "order1",
    "timestamp": "2022-01-01T00:00:00Z",
    "items": [
      { "id": "item1", "name": "item1", "price": 10, "quantity": 1 },
      { "id": "item2", "name": "item2", "price": 20, "quantity": 2 }
    ]
  }
}

But we don't know if there's already a record exists for user1. Here's a python code snippet that first checks if the record exists, and if exists append the order to the users orders array. If not create a new document for the user.

import json

from elasticsearch import Elasticsearch
from elasticsearch.exceptions import NotFoundError

es = Elasticsearch(hosts=["http://localhost:9200"])


def update_or_insert(body):
    doc_id = body["username"]
    try:
        res = es.get(index="orders", id=doc_id)

        # Update
        updated_body = {
            "script": {
                "source": "ctx._source.orders.add(params.order)",
                "lang": "painless",
                "params": {"order": body["order"]}
            }
        }
        es.update(index="orders", id=doc_id, body=updated_body)
    except NotFoundError:
        res = es.index(index="orders", id=doc_id, body=body)
    return res


if __name__ == "__main__":
    data = {
        "username": "user1",
        "order": {
            "id": "order1",
            "timestamp": "2022-01-01T00:00:00Z",
            "items": [
                {"id": "item1", "name": "item1", "price": 10, "quantity": 1},
                {"id": "item2", "name": "item2", "price": 20, "quantity": 2},
            ],
        },
    }
    print(update_or_insert(data))

Option 2

Use upsert, which will create the document if not exists or update if exists, which is one single API call.

Here's a sample python code that demonstrate the upsert operation:

import json

from elasticsearch import Elasticsearch
from elasticsearch.exceptions import NotFoundError

es = Elasticsearch(hosts=["http://localhost:9200"])

def upsert(body):
    updated_body = {
        "script": {
            "source": "ctx._source.orders.add(params.order)",
            "lang": "painless",
            "params": {"order": body["order"]}
        },
        "upsert": {
            "username": body["username"],
            "orders": [body["order"]]
        },
        "scripted_upsert": True
    }
    res = es.update(index="orders", id=body["username"], body=updated_body)
    return res


if __name__ == "__main__":
    data = {
        "username": "user1",
        "order": {
            "id": "order1",
            "timestamp": "2022-01-01T00:00:00Z",
            "items": [
                {"id": "item1", "name": "item1", "price": 10, "quantity": 1},
                {"id": "item2", "name": "item2", "price": 20, "quantity": 2},
            ],
        },
    }
    print(upsert(data))

Codes can be found in this repo: github.com/tanjibpa/es-upsert